Comparative mass spectra analysis as a steppingstone towards a better understanding of the origin and evolution of Saturn’s rings

The origin and chemical evolution of Saturn’s rings remain debated. Proposed formation scenarios include the disruption of an icy moon, tidal splitting of a comet, or primordial formation followed by long-term processing, including contamination by exogenous dust (Crida et al. 2019). We propose that direct intercomparison of mass spectrometer datasets could further our understanding of similarity or dissimilarity of organic matter reservoirs, even when full spectral deconvolution is not possible because of limited mass resolution and degeneracy among possible constituents. Here, we take a first step by comparing Ion and Neutral Mass Spectrometer (INMS) data (Miller et al. 2020), obtained during Cassini’s proximal orbits from material flowing from the rings into Saturn’s upper atmosphere (Waite et al. 2018), with Rosetta’s Double Focusing Mass Spectrometer (DFMS) measurements from the dusty coma of comet 67P/Churyumov-Gerasimenko (Hänni et al. 2022), as well as with laboratory spectra from irradiation experiments with astrochemical ice analogues (Javelle et al. 2025; Danger et al. 2013).

A first comparison between the averaged unit-resolution INMS spectra and rebinned DFMS spectra reveals striking similarities, including broad intensity patterns arising from a wide range of organic molecules and the prominent m/z = 91 peak associated with aromatic benzyl-bearing compounds such as toluene. Differences occur mainly at higher masses and in heteroatom-bearing regions. Some variability in fragmentation patterns between the datasets is expected, for example because the spacecraft had very different relative velocities, but remains difficult to quantify. Our preliminary analysis suggests that the equatorial ring inflow material may be related to 67P-like matter. A reference dataset of micrometeorites and/or interplanetary dust particles is needed to further constrain the various origin and evolution scenarios. Comparison with irradiated ice residue, to test a link to radiation-driven processing in these two reservoirs of organics, is ongoing. Similarity among all these organic matter reservoirs could indicate a shared history in the early Solar System.

 

Crida et al. Nat. Astron. (2019) 3, 967-970.

Waite et al. Science (2018) 362, eaat2382.

Miller et al. Icarus (2020) 339, 113595.

Hänni et al. Nat. Commun. (2022) 13, 3639.

Javelle et al. CommChem (2025) 8, 306.

Danger et al. GCA (2013) 118, 184-201.